Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. In general, the wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
With the advent of various communication systems, a heterogeneous network environment in which various cells coexist in a local area is taken into account. For example, a micro cell having relatively low power transmit power (e.g., a pico cell, a femto cell, etc.) exists in the coverage of one macro cell. In addition, a cell can be classified into an open access (OA) cell which can receive a service any time when necessary without additional access restriction and a closed subscriber group (CSG) cell of which access is allowed for only a specific user.
Interference between heterogeneous cells may occur seriously in the heterogeneous network. A transmit power difference between the cells results in a signal characteristic in which a serving cell selected according to received signal power is weaker than a neighbor cell due to a path loss.
For example, it is assumed that a macro user equipment (UE) belonging to a macro cell approaches to a micro cell. An uplink signal of the macro UE may strongly interfere to the micro cell. In addition, a downlink signal of the macro cell may have weak signal strength due to interference with the micro cell neighboring to the macro UE. In particular, if the neighbor micro cell is a CSG cell, it is difficult for the macro UE to move to the micro cell, and thus the macro UE may experience serious deterioration in a communication service.
Accordingly, there is a need for mitigating inter-cell interference in a wireless communication system in which various cells coexist.